The present invention relates to a system and method for electrical stimulation of salivation and, more particularly, to a system and a method of using same for electrically detecting a lack of saliva in the oral cavity and for electrically stimulating the oral cavity so as to induce the production of saliva from the salivary glands.
Saliva performs many critical functions in the oral cavity and is essential for the maintenance of oral health. The accomplishment of the functions of saliva depends on proper salivary production. Saliva neutralizes acid that promotes dental caries and aids in the remineralization of areas of incipient caries development. Saliva contains specific antifungal agents and reduces bacteria in the oral cavity by a number of means including dilution, aggregating factors, and microbicidal enzymes. Salivary glycoproteins reduce intraoral trauma (between different oral structures such as teeth, cheek, tongue and lips) by lubricating the hard and soft tissues and saliva aids swallowing by facilitating bolus formation. Salivary enzymes such as lipase and amylase start the digestion of food. Taste perception is facilitated by salivary dilution and delivery of food particles to the taste buds.
Saliva is produced by the salivary glands. Each individual has three pairs of salivary glands: the parotid glands (the largest, which lie under the skin of the cheeks), and the submandibular and the sublingual, which are located at the floor of the mouth. The secretion of saliva is regulated by the autonomic nervous system.
Xerostomia, or dry mouth, is a very common complaint. While between 20-30% of the adult population may complain of it at some time, for 1-2% of the population it is a serious problem. The chronic lack of saliva is associated with rampant, severe dental caries, difficulty chewing, painful swallowing, diminished taste and smell, and oral fungal infections.
Xerostomia can result from many different causes. The most prevalent is as a side effect of one or more medications that inhibit salivation through anticholinergic or other mechanisms. Hundreds of drugs are known to have this side effect, especially antidepressants, MAO inhibitors, neuroleptics, parasympatholytics, some analgesics and certain combinations of anti-hypertensive agents. A variety of autoimmune disorders, particularly, Sjogren's syndrome, are another important cause. One to three million Americans suffer from Sjogren's syndrome. Severe salivary gland hypofunction also results from therapeutic irradiation of the head and neck as well as other causes including other diseases such as sarcoidosis, amyloidosis, graft-versus-host disease, HIV infection, diabetes, Alzheimer disease, depression, dysautonomia and Fabry disease. Aging itself appears to be a cause of xerostomia as well.
Treatment of xerostomia is difficult and while there are some currently available treatments, they are not satisfactory. Symptomatic treatments include sialogogues such as sugarless hard candies or chewing gum. Symptomatic palliative relief can sometimes be obtained by frequent sips of water or use of a saliva substitute. In patients whose xerostomia has a non-pharmacologic cause, oral pilocarpine (if not contraindicated) may be helpful but has the side effects of perspiration, flushing, urinary urgency and lacrimation.
It is well known that it is possible to increase salivation by stimulation of the salivary glands by low power electric current. Studies have demonstrated that the salivary glands respond to discrete stimulatory pulses with increased salivation (Weiss et al J Oral Maxillo-facial Surg 44:845-50, 1996; Steller et al J Dental Res 67: 1334-7, 1988; Talal et al Rheum Int 12:43-5, 1992)
U.S. Pat. Nos. 4,519,400 and 4,637,405 to Brenman et al teach a device and method for electrical induction of salivation. The device includes a housing which may be received in the oral cavity of a user, the housing enclosing electronic signal generating means and electrodes for applying a signal to neurally sensitive locations of the oral cavity to induce salivation. The device can be held in the oral cavity of the user for a period of time and be removed therefrom and to be reinserted later, or it can be fixed to the palate by clips fitted around molar teeth of the upper jaw. In its method aspect the invention involves stimulation of salivation by the application of an electrical signal to neurally sensitive locations
EP 278847 relates to an apparatus for stimulating the secretion of saliva and has the form of a pellet made of a non-conductive material with electrodes on opposite faces thereof. The apparatus has no means of firm attachment within the mouth and is only held freely within the mouth and is moved from one place to another by aid of the tongue. In addition, as with the devices of Brenman et al, none of these devices can be operated by either remote or feedback control.
WO 00/44439 teaches a device and method for inducing salivation using an implanted device. Several generations of the device of the invention are envisaged including those with controllable or changeable electrical parameters, and those where changing the parameters is under the control of a salivation sensor which constantly senses mouth humidity and forms a feedback loop with the device. The invention does not however disclose how such control can be accomplished and is not enabling as to how such a salivation sensor might operate and how feedback control can be effected.
There is thus a widely recognized need for, and it would be highly advantageous to have, a system and method for electrical stimulation of salivation devoid of the above limitation.